Direction finding antenna system



Dec. '1, 1936. H. G. B USIGNIES 2,062,441

v DIRECTION FINDING ANTENNA SYSTEM Filed 001;. 29, 1931 FIG.

INVE'NTOR 19.6. BUS/GN/ES A TTORNEV.

Patented Dec. 1, 1936 UNITED STATES PATENT OFFIE DIRECTION FINDING ANTENNA SYSTEM Application October 29, 1931, Serial No. 571,720 In France November 21, 1930 Claims.

This invention relates to improvements in aerial systems and more particularly to improvements in aerial systems having directional properties.

Transmitting or receiving aerial systems having directional properties are commonly used in high frequency signaling systems, and in such aerial systems it is generally desired to have only one privileged direction or directive pattern.

An object of the present invention is to obtain substantially the same shape of directional diagram for an aerial system over a substantial range of frequencies.

In accordance with one feature of the invention, a number of aerial systems of different types are combined and the inherent properties of said different types of aerial adjusted so as to obtain for the combined system a directional diagram (in one plane or in space) of predetermined shape over a substantial range of frequencies.

In accordance with another feature of the invention, the directional diagram of an aerial system comprising, for example, an ordinary, tuned non-directional antenna in combination with a tuned frame aerial or other radio directive element, is rendered substantially constant over a substantial range of frequencies by linking together the tuning systems with the phase correcting system of the antenna and/or of the frame aerial.

The following description refers particularly to the combination of antennas and frame aerials as used in radio direction finders but it should be noted that the broad principle of the invention could likewise be embodied in other constructions using, for instance, radiators and/or reflectors as used in short and ultra short wave high frequency signaling systems. The present invention would in such a case permit the same aerial system to be used for transmitting and/or receiving a plurality of wave lengths without modifying the configuration of the aerial system.

Referring now more particularly to aerial systems used in radio direction finders, it is known that such systems usually consist of antennas associated with frame aerials,'the directional diagram of the combined aerial having generally the shape of a cardioid curve for the wave length for which the aerial system is adjusted. In such systems, the shape of the cardioid is different for different wave lengths so that whenever it is desired to determine the bearings of stations having different wave lengths from those for which the aerial system is adjusted, separate adjustments for determining the bearings of said.

stations are necessary. This is a very important drawback in the case of automatic direction finders in view of the amount of time necessary for making a separate adjustment in order to avoid the ambiguity of 180 to which such direction finders are subjected. This modification in the shape of the directional diagram of the combined aerial as a function of the received wave length is due to a variation in the ratio antenna effect frame efi'ect as a function of the wave lengths. The variation of this ratio is due to the following phenomena:

The electro-motive force induced in the antenna by an electro-magnetic field set up, for instance, by a transmitting station is 90 out of phase with regard tothe electro-motive force induced by the same electro-magnetic field in a frame located in space at approximately the same place as the antenna. If the frame aerial is tuned as well as the antenna, it will be seen that before combining the currents set up therein it is necessary by some means to change the phase of the current by 90 either in the antenna or in the frame; this effect is usually obtained in part by means of an inductive coupling between the antenna and the frame.

It should be noted that for a given intensity of the current traversing the antenna circuit, the electro-motive force induced by this current in the circuit of the frame aerial will vary proportionately to the frequency of the said current. On the other hand, the effective height of the frame will also vary proportionately to the frequency whereas the effective height of a small antenna remains substantially constant within limits over a constant band of frequencies.

Assuming that it is desired to obtain for an aerial system comprising an antenna associated with the frame aerial, a directional diagram having substantially the shape of a constant cardioid curve over a wide range of frequencies, the following conditions should be fulfilled; (1) a constant ratio should be maintained between the electro-motive force in the frame and the electromotive force induced in the circuit of the frame aerial by the circuit of the antenna, (2) the high frequency current circulating in the antenna oscillation circuit should be in phase with the electro-motive force set up in this antenna, thus necessitating that the oscillation circuit of the antenna be tuned to the frequency of the signals. Thus, this current will set up in the circuit of the 2 frame an electro-motive force of the same phase as that induced directly in this circuit by the impinging electro-magnetic field so that these 'electro-motive forces add algebraically.

frames varies proportionally to the frequency.

the inductive coupling between-the-antenna and the frame sets up in the circuit of the frame aerial an electro-motiveforce varying in the same conditions.

One way for obtaining constantly the same 7 phase relation between the currents set up in the antenna and in the frame aerial inspite of vari- -ations in the received frequencies is to vary the tuning of the antenna circuit at the same time as the tuning-of the frame circuit. In order to .obtain this effect the following arrangement is rprovided in accordance with a feature of the present invention; The tuning condenser of the :frame aerial isadapted to drive the adjustable tuning condenser of ;the;antenna circuit, this adjustable condenseribeing chosen with a suitable ;m a'ximum-capacityand with a curve of variation of capacity suitable for attaining the result in view.

' Another system more a less similar consists 1 in providing on the shaftof the tuning condenser of the .frameiaerial a commutator comprising a pluralityof contacts, said commutator being adapted to insert in the antenna tuned circuit fixedcapacitiesih addition to an initial capacity,

the values of the said capacities being suitably Idetermined'eitherby computation or by experiments. With such a system the capacity variations are not continuous and in order to avoid zsharp variations of phase near the points of exact ituning, .it is advisable to damp the oscillation circuit includedin the antenna by means of "a resistance' of appropriate value.

In order to obtain greater precision in the adjustmentof the amplitudes of the currents received in the frame aerial and in the antenna,

a resistance :of suitable value may be inserted in series with each additional capacity intro- "ducedinithe' circuit by means of commutators. Likewise, in'order'to obtain suitable phase rela- :tion ,tit'is possible to vary the inductanoes of the antenna circuit whilst leaving the tuning capacity at a fixed value or to vary simultaneously the inductances and the capacity and/or to "change thedamping' resistance of the tuned cir- 'cuit. It will be clear that the number of contacts provided on the commutator adapted to insert capacities in the antenna tuned circuit will determine, to a certain extent, the precision with which thediagram of the aerial system will remain constant inshape over a given frequency range. -several different frequency bands, it is possible If the same tuning condenser is used for r use a similar arrangement by inserting inductan ces of suitable value by means of a commutator similar} to' the one already mentioned;

this {commutator 'providing at the same time the adjustment of the inductances of the'a'ntenna ined f tadapted to insert damping resistances in the tuned circuit.

The commutator may also be An embodiment or the invention is illustrated by way of example in the accompanying d awing wherein:

Fig. 1 represents an aerial system comprising an antenna and a frame aerial associated with means for obtaining a directional diagram of predetermined shape over a suitable frequency band;

Figs. 2 and 3 illustrate modifications of the arrangement illustrated in Fig. 1.

Referring to Fig. 1 a receiving antenna is shown in A and a frame aerial in F. The frame aerial F and the antenna A are inductively coupled by means of inductances LA, LF and LF'. In the present case the inductances of the frame aerial circuit are divided into two parts LF and LF, in order to keep the frame aerial as symmetrical (electrically) as possible. The antenna tuned circuit consists of capacities C associated with the inductances LA. These capacities may be varied by rotating the switch S. It will be noted that the shaft of switch S is coupled by a mechanical link M1. to the shaft of the tuning condenser CF of the frame F.

It will be seen that the mechanical link between the tuning system of the frame F and the phase correcting system of the antenna permits by suitable selection of the capacities C and CF to obtain a directional diagram for the aerial system comprising the frame F and the antenna A of substantially constant shape over a predetermined. frequegnctv range. A resistance R may be inserted in the antenna tuned circuit in order to avoid the sharp variation of phase due to the change of capacity C. This resistance has the effect of damping the antenna tuned circuit. The aerial system A and F may be associated with any kind of device such as a direction finder DF.

The capacities C shown in Fig. 1 are chosen of such values that the antenna A can be tuned to a plurality of wave lengths to be received. Further, the coupling between LA and LF is chosen in such a way that the oscillating current in the antenna circuit sets up in the circuit of the frame F an electro-motive force equal to the electromotive force induced in the circuit by the impinging electro-magnetic field when the frame F is directed with regard to the sending station so as to obtain maximum intensity of the received signals. The tuning system of the antenna A and of the frame F are coupled, for instance, mechanically so that the tuning positions of the antenna circuit correspond to the tuning positions of the frame circuit for a predetermined band of frequencies whilst the coupling between LA and LF is adapted to vary with the frequencies of the signals to be received so that the effect of the variation of the effective heights of the frame F is compensated by the variation with frequencies of the coupling between LA and LP.

The phase correcting system associated with the antenna A is shown within the dotted rectangle in Fig. 1 and consists of a variable capacity C comprising a plurality of fixed condensers as illustrated in Fig. l or the phase corrector may comprise a variable inductance LA as shown in Fig. 2 or of a variable capacity C as shown in Fig. 3.

It has been explained above how a reception diagram of constant form may be obtained for an H. F. power collecting system.

In certain cases it is necessary to obtain another curve than a cardioid, which may be of such a form that when the collector system is used with a direction finder of the type mentioned above, no induced E. M. F. may be said to be obtained in the frame when the latter has its plane in the direction of propagation of the electro-magnetic field of the transmitting station and that at as small an angle as possible. This result may be disguised in a direction finder employing a frame by a parasitic antenna effect in said frame or by an abnormal polarization of the electro-magnetic field.

In order to compensate for the persistent parasitic effect, when the plane of the frame is in the direction of propagation of the electro-magnetc field of the station under consideration, means are provided, according to one of the characteristics of the invention, to cancel the E. M. F. due to said parasitic effect by an opposite E. M. F. derived from the circuit of an associated antenna, which may also be the antenna mentioned at the beginning of the present specification. The compensating M. F. can be obtained by coupling, by induction, a small inductance included in the circuit of said associated antenna with an inductance included in the circuit of said frame. By adjusting the coupling and/or one or both of the above mentioned inductances, it is possible to cancel the parasitic effect.

Although the. invention has been described with particular reference to direction finders, it should be noted that the invention could be embodied in structures widely different from those herein described without departing from the spirit of the present invention.

What is claimed is:

1. In a direction finding system, an open nondirectional antenna, the effective height of which is relatively constant over a wide band of frequencies, a closed directional aerial, the effective height of which varies with frequency, a circuit for tuning said antenna comprising an inductance and an adjustable condenser connected in shunt thereto, a plurality of inductances coupled to said inductance, a direction finder, one of the plurality of inductances being included between one terminal of the aerial and the direction finder and another of said plurality of inductances being included between the other terminal of the aerial and the direction finder, an adjustable condenser connected between the two last mentioned inductances, and means for simultaneously varying said condensers, the diiference in capacity variation of said condensers corresponding in effect to the difference in variation with frequency of the antenna impedance and loop aerial impedance.

2. In a direction finding system, an open nondirectional antenna, the effective height of which is relatively constant over a wide band of frequencies, a closed directional aerial, the effective height of which varies. with frequency, a circuit for tuning said antenna comprising a resistance and an inductance connected in series and an adjustable condenser connected in shunt to said re sistance and said inductance, a plurality of inductances coupled to said inductance, a direction finder, one of the plurality of inductances being included between one terminal of the aerial and the direction finder and another of said plurality of inductances being included between the other terminal of the aerial and the direction finder, an adjustable condenser connected between the two last mentioned inductances, means for simultaneously varying the adjustable condensers, the difference in capacity variation of said condensers corresponding in eifect to the difference in variation with frequency of the antenna impedance and loop aerial impedance.

3. In a direction finding system, an antenna, a frame aerial, a tuned circuit connected to said antenna comprising an adjustable inductance and a condenser connected in shunt thereto, a plurality of inductances coupled to said inductance, a direction finder, one of the plurality of inductances being included between one terminal of the aerial and the direction finder and another of said plurality of inductances being included between the other terminal of the aerial and the direction finder, an adjustable condenser connected between the two last mentioned inductances, means for simultaneously varying the adjustable inductance and the adjustable condenser.

4. In a direction finding system, an antenna, a frame aerial, a tuned circuit connected to said antenna comprising a resistance and an adjustable inductance connected in series and a .con-

denser connected in shunt to said resistance and inductance, a plurality of inductances coupled to said inductance, a direction finder, one of the plurality of inductances being included between one terminal of the aerial and the direction finder and another of said plurality of inductances being included between the other terminal of the aerial and the direction finder, an adjustable condenser connected between the two last mentioned inductances, and means for simultaneously varying the adjustable inductance and adjustable condenser.

5. In a direction finding system, an antenna, a frame aerial, a tuned circuit connected to said antenna comprising an inductance connected in series with said antenna, a plurality of condensers, a plurality of inductances coupled to said inductance, a direction finder, one of the plural ity of inductances being included between one terminal of the aerial and the direction finder and another of said plurality of inductances being included between the other terminal of the aerial and the direction finder, an adjustable condenser connected between the two last mentioned inductances, and means for simultaneously varying said adjustable condenser and for connecting a different number of said plurality of condensers in shunt to the first mentioned inductance.

6. In a direction finding system, an antenna, a frame aerial, a tuned circuit connected to said antenna comprising a resistance and an inductance connected in series, a plurality of condensers, a plurality of inductances coupled tosaid inductance, a direction finder, one of the plurality of inductances being included between one terminal of the aerial and the direction finder and another of said plurality of inductances being included between the other terminal of the aerial and the direction finder, an adjustable condenser connected between the two last mentioned inductances, and means for simultaneously varying said adjustable condenser and for connecting a difierent number of said plurality of condensers in shunt to the first mentioned inductance.

7. In a direction finding system, an open nondirectional antenna, the efiective height of which is relatively constant over a wide band of frequencies, a closed directional aerial, the effective height of which varies with frequency, a circuit for tuning said antenna comprising an inductance and an adjustable capacity device connected in shunt thereto, a plurality of inductances cou pled to said inductance, a direction finder, one of the plurality of inductances being included between one terminal of the aerial and the direction finder and another of said plurality of inductances being included between the other terj minal of the aerial and the direction finder, an

adjustable capacity device connected between the twoilast mentioned inductances, and means for simultaneously varying said devices, the difference in capacity variation of said devices corresponding in efiectrt'o the difference in variation with frequency of the antenna impedance and loop aerial impedance.

. 8.v In a direction finding system, an open nondirectional antenna, the effective height of which is relatively constant over a wide band of frequencies, a closed directional aerial, the effective height of which varies with frequency, a circuit for tuning said antenna comprising an inductance and an adjustable impedance device connected in shunt. thereto, a plurality of inductances coupled to said inductance, a direction finder, one of the plurality of inductances being included between-oneterminal of the aerial and 'thedlre'ction. finder and another of said plurality 10f inductances'being included between the other terminalof the aerial and the direction finder, an adjustable impedance device connected between the two last'mentioncd induotances, and

means forsimultaneously varying said devices, the difference in impedance variation of said devices corresponding in effect to the difference I in variation with frequencyof the antenna impedance andloop aerial impedance. 9. A directional aerial system comprising at :least two component aerials of difierent types including an open'antenna-and aframe aerial, the

- tuning of'said component aerials, as well as the "phase'relation of the currents flowing therethrough being simultaneously adjusted by ganging together mechanically adjustable impedance elements comprising adjustable condensers provided in the' circuit of said component aerials,

' the value of said-impedance elements and the variation laws thereof with frequency being chosenso as to constantly obtain for the combined aerial system, a directional diagram of predetermined shape. over a substantial range of frequencies, the damping of the tuned circuit associated with said open antenna being varied at the same time as the adjustable ganged con- ;densers of the said open antenna and of the said contact members operatively connected with a plurality of fixed condensers, said condensers being connected incircuit with said non-directional antenna and having such capacities as to obtain a directional diagram for said aerial system of substantially constant shape over a predetermined range of frequencies.

11. An aerial system comprising a non-directional antenna, a directional antenna, and means simultaneously controlling the phase and magnitude of currents in said antennae, said means including switch means having a plurality of contact members operatively connected with a plurality of inductances, said inductances being connected in circuit with said non-directional antenna and of such value and number as to obtain a directional diagram for said aerial system of substantially constant shape over a predetermined range of frequencies.

12. A directional aerial system including a nondirectional antenna, a directional antenna, and common controlled resistance and reactance means operatively linked together and connected with said antennae for simultaneously adjusting the phase and amplitude of currents in said antennae and for constantly obtaining for said aerial system a directional diagram of substantially constant shape over a substantial range of frequencies.

13. A directional aerial system including a non-directional antenna, a directional antenna, and simultaneously controlled resistance and reactance means connected with said antennae, operatively linked together, and having selected values with frequency variations to constantly obtain for said aerial system a directional diagram of substantially constant shape over a substantial range of said frequency variations.

14. A directional aerial system comprising a nor-directional antenna circuit including variable resistance means therein and variable reactance tuning means therefor, a directional antenna circuit including variable reactance tuning means therefor, and means for simultaneously controlling said resistance means and the plurality of said reactance means and for constantly obtaining for said aerial system a directional diagram of substantially constant shape over a substantial range of frequencies.

15. A directional aerial system comprising a non-directional antenna circuit including variable resistance means therein and variable reactance tuning means therefor, a directional antenna circuit including variable reactance tuning means therefor, and means for simultaneously controlling said resistance means and the plurality of said reactance means and for constantly obtaining for said aerial system a directional diagram of substantially constant shape over a substantial range of frequencies, said resistance means including a plurality of resistances connected with said non-directional antenna circuit.

HENRI G. BUSIGNIES. 

